Which song has the longest continuous note?

Excluding the old (Medieval) "clausulae" in which singers would improvise a line of melismas over another singer's pedal point (as in some of the works of Perotin), the longest note in any piece that I could think of for a singing voice is the 8.5-measure long high A for soprano voices in the choral finale of Beethoven's 9th symphony (I measured its duration in my score). This note usually takes about 11-12 seconds to sing, which on a note that high (880 VPS) is quite difficult for most choristers. Note that I could be extremely wrong about this.

Written or interpreted?

In UK chart history:

Longest Note Held In A Hit -- This record is held by Morten Harket, lead singer with group A-Ha. In "Summer Moved On" (no. 33, June 2000) he holds a vocal note for 20.2 seconds.

http://www.everyhit.com/record7.html

https://en.wikipedia.org/wiki/Morten_Harket

Usher -- The sexy, suave singer says he would like to break another Guinness World Record by holding the longest note ever. He expects to achieve his goal on Broadway. Now he wants to hold the title to an existing long note record, which is currently at 26 seconds. Apparently, he is at 21-and-a-half (seconds) right now.